$ { {2} \times \left[\begin{array}{rr}{0} & {-1} \\ {1} & {1}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{2}\times{0} & {2}\times{-1} \\ {2}\times{1} & {2}\times{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{0} & {-2} \\ {2} & {2}\end{array}\right]}$